A set of 3D printed steel polyhedral dice that I've been working on intermittently for the last couple of years. Created in Blender. The largest is 3cm from face to face. The D20 has been balanced so that each face has as close to the same mass as possible within the limitations of the printer. These can be purchased at my shop on Shapeways.com.
You can get some technical specs on the material here.
In my own experience it's really solid.